Not sure if I am going to be shot down with this. I'll kick it off to get the debate going with:
Keep it short, concise and professional. The cover letter is should simply state what position you are after. Don't talk abut availability. Your CV tells them if you maybe suitable. Stick religiously to the correct format with date top right. Full recipient details left/ Full sender details right. Contact detail (phone/email/etc) underneath sender address right hand side.
As for the letter bit:-
Dear Capt Richards,
Please find my Curriculum Vitea enclosed for the position of Junior First Officer.
Should you require further information or have any queries then please feel free to contact me at any time.
Yours sincerely,
XXX
Alternatively:
Dear Madam or Sir,
Blah, blah.
Yours faithfully,
XXX
The big question is. Hand-written or type written. To determine that I would say that if the letter goes to a department then type written. If it goes to an individual then hand written. Difficult one that.